This application relates generally to communications networks, and more particularly, to predicting the performance of telephone lines when transmitting data.
Public switched telephone networks, i.e., plain old telephone systems (POTS), were originally designed for voice communications having a limited frequency range. Today, the same POTS lines often carry data transmissions. Since data transmissions generally have different frequency properties, a POTS line that works well for transmitting voice may work poorly for transmitting data. Since POTS lines may not work well for data transmissions, both telephone operating companies (TELCO's) and customers want tests for predicting which lines can transmit data.
In the past, telephone operating companies (TELCO's) performed pre-qualification and pre-disqualification tests on POTS lines prior to connecting data transmitters to them. These tests identified some situations where the line can or cannot support data transmissions without remedial actions. But, the pre-qualification and pre-disqualification tests both produced a significant number of mispredictions, i.e., false positives and false negatives.
More critically, current pre-qualification tests for POTS lines are frequently not automated and consequently labor intensive. Often, they demand skilled interpretations of high frequency parameters of a line to determine its data transmission capabilities at high speeds. The tests do not make full use of automated testing systems, e.g., as described in U.S. Pat. No. 5,699,402, which is herein incorporated by reference in its entirety. At a network scale, such tests would be very expensive to implement.
Furthermore, as data transmission demands increase, simple pre-qualification or pre-disqualification is no longer sufficient. Now, customers also want information enabling them to choose between competing options for transmitting data. Instead of simple qualification or disqualification, the customer frequently wants to know which transmission medium and/or devices will work better. Simple pre-qualification does not provide customers with a way to compare the different viable options for transmitting data.
The present invention is directed to overcoming or, at least, reducing the affects of one or more of the problems set forth above.